1. Field of the Invention
The invention relates to a detection device for a motor vehicle for detecting wetness on a roadway. The device has a moisture-detection unit and an evaluation unit that is designed to determine wetness on the roadway on the basis of a moisture value that is detected by the moisture-detection unit. The invention also relates to a method for detecting wetness on a roadway.
2. Description of the Related Art
Wetness on a roadway constitutes a high hazard potential for motor vehicles since aquaplaning can occur and hazardous situations can arise as a result of veering off of the vehicle, as a function of the quantity of moisture and the speed of the motor vehicle.
Sensors therefore are developed to determine or estimate the risk of aquaplaning for a motor vehicle in a simple way. Known systems use signals of rain sensors in the front windshield and the corresponding wiper activities to estimate the moisture on the roadway. However, such systems are subject to an uncertainty since the detected moisture on the front windshield can be thrown up by vehicles traveling in front or precipitation occurring in the stationary state of the motor vehicle cannot be detected.
Other communication systems warn of hazards due to aquaplaning in which other vehicles detect the hazard and make available a hazard warning, for example via a radio link. However, such systems have a delay in the warning and require at least one vehicle that has entered the hazardous situation to communicate a corresponding warning.
A corresponding hazard warning in navigation maps does not take into account the current weather situation. Thus, such systems also have large uncertainty.
DE 10 2010 063 017 A1 discloses a driving assistance system for detecting wetness on a roadway, in which system a trail of spray of the motor vehicle is detected by a camera and the risk of aquaplaning is estimated on the basis of the trail of spray. A disadvantageous of this system is that the technical expenditure for the driving assistance system is very high, and the detection of the trail of spray at the rear results in a delay in the measurement, and hence a further uncertainty factor.
The object of the invention is therefore to provide an improved device for a motor vehicle which can determine wetness on a roadway with little technical expenditure and increased reliability. In addition, an object of the invention is to make available a corresponding method for detecting wetness on a roadway.